In a Long Term Evolution (Long Term Evolution (LTE)) system, a User Equipment (User Equipment (UE)) needs to acquire Downlink Control Information (Downlink Control Information (DCI)) configured by an Evolved NodeB (Evolved NodeB (eNB)) for the user equipment before receiving or transmitting service data, the DCI is carried on a Physical Downlink Control CHannel (Physical Downlink Control CHannel (PDCCH)). Generally, one PDCCH is aggregated by 1, 2, 4, or 8 continuous Control Channel Elements (Control Channel Element (CCE)), and each aggregation level corresponds to a search space, the aggregation level represents the number of CCEs by which the PDCCH is aggregated, and the search space is a set of PDCCHs to be detected by the UE, for example, the search space with the aggregation level of 4 is a set of PDCCHs which includes all PDCCHs aggregated by 4 CCEs and to be monitored by the UE. The search space may include Common Search Space (Common Search Space (CSS)) and UE Specific Search Space (UE Specific Search Space (UESSS)).
In order to decrease the delay of user's plane, in the Long Term Evolution Advanced (Long Term Evolution Advanced (LTE-A)) system, a Contention Based (Contention Based (CB)) uplink transmission solution is proposed, that is, the base station allocates a same uplink resource to a group of uplink synchronization users (i.e., a CB user group) dynamically by Contention Based uplink Grant (Contention Based uplink Grant (CB Grant)) information at each Transmission Time Interval (Transmission Time Interval (TTI)). The so called CB Grant is downlink control information carried on the PDCCH and is used for granting information required by the contention based uplink transmission, including the allocated uplink time-frequency domain resource information, Modulation and Coding Scheme ((MCS) Modulation and Coding Scheme) and so on. In the CB uplink transmission solution, when there is uplink data to be transmitted, users in the CB user group needn't to send Scheduling Request Indicator ((SRI) Scheduling Request Indicator) in advance, they only need to monitor the CB Grant and then directly use the granted CB resource (for example, the allocated uplink time-frequency domain resource) to transmit uplink data or report Buffer Status Report ((BSR) Buffer Status Report).
In the above CB uplink transmission method, the delay of the user's plane cannot be decreased because the overhead of the CB Grants is large and the PDCCH scheduling blocking is easy to occur, that is, the CB Grants are hard to be scheduled.